The following code fails to compile (using VS2010) and I don't see why. The compiler should be able to infer that List is 'compatible' (sorry for lack of a better word) with IEnumerable, but somehow it doesn't. What am I missing here?

interface ITest {
    void Test();
}


class TestClass : ITest {
    public void Test() {
    }
}

class Program {
    static void Test(IEnumerable<ITest> tests) {
        foreach(var t in tests) {
            Console.WriteLine(t);
        }
    }
    static void Main(string[] args) {
        var lst = new List<TestClass>();

        Test(lst); // fails, why?

        Test(lst.Select(t=>t as ITest)); //success

        Test(lst.ToArray()); // success
    }
}